Wait...im confused...or just plain dumb. But are you saying the arbor is a lil bit too small for the barrels arbor hole? Like its loose and has play? Cuz ive had one revolver like that and i degreased it well, lightly sanded and placed a thin smear of jb weld on the area that seemed to be thinner...that made the arbor "thicker" and then i sanded it down just enough to give it a tight fit to the barrel. Worked great. At first i used a thin .002 inch copper sheet...cut a small shim and let it stick to the side of the arbor when i would put the barrel on, this made a tight fit but i didnt want to mess with it everytime i took it apart. So thats when i came up with the jb weld solution. But again...this only works if im understanding the problem youre explaining correctly